This application proposes a multidisciplinary collaborative approach to investigating the intracellular signaling pathways critical to cardiocyte function in human heart failure. The overall application is based on three working hypotheses. First, that abnormalities in calcium cycling proteins and myofibrillar function contribute significantly to the pathogenesis of heart failure. Second, that although the signaling pathways regulating calcium signaling and myofibrillar function can be altered in response to common hemodynamic or humoral stimuli, they are distinct and separable on a molecular level. Third, that somatic gene and/or protein switching transfer will allow us to alter the phenotype of myocytes in human heart failure. Essential to the success of this proposal is the ability to perform manipulations in human cardiac fibers and myocytes. Using adenoviral gene transfer, we can modulate specific signaling pathways of calcium metabolism in human heart failure. Understanding the specific signaling pathways that modulate cardiocyte function, developing approaches to localize modulation of these proteins, and evaluating their functional contribution to the progression of heart failure are the ultimate goals of this R01 competing renewal. We believe the interdisciplinary effort will contribute to an improved understanding of the pathophysiology of heart failure and ultimately, the development of novel therapeutic strategies for this important clinical condition.